Polygon square



Aug. 24, 1943. H. B. HlDY 2,327,892

POLYGON SQUARE Filed March 19, v1942 ATTDRIVEy Patented Aug. 24, 1943 UNITED STATES PATENT OFFICE POLYGON SQUARE Herald B. Hilly, Wentzville, Mo.

7 Application March 19, 1942, Serial No. 435,376

3 Claims.

This invention relatesto drafting instruments, and is herein referred to generally as a polygon square. The general object, nature and purpose of the invention is to provide a drafting instrument in the nature of a combination square and compass for describing polygons and circles expeditiously and accurately.

A further object is to provide an instrument of the kind referred to, the same being generally T-shaped in plan, the upper stem being in the form of an elongated, straight, edged work bar or lay-out bar, right angled in cross-section and including a relatively narrow and fiat blade, web or rail designed for horizontal disposition'upon the work, and demarked orcalibrated upon its proposed upper side or face, from the outer ends thereof inwardly to its center point, with a plurality of spaced and numbered calibrations, for laying out the lengths of the sides of polygons of various size or area, as may be required to complete the figure, this blade or rail being hereinafter referred to as the polygon blade or rail, the device including a similar flat blade or rail of equal length and thickness, preferably integrally formed with the polygon blade and extended at right angles thereto along the proposed rear margin thereof, this latter blade being hereinafter referred to as the circle blade or rail, and being also demarked with a plurality of calibrations consecutively numbered from its center point outwardly to the ends thereof, ac-

cording to a plan and purpose later to be described; the medial lower stem of the instrument being extended perpendicularly from theexact center of the rear side of the unit formed by the combined polygon and circle rails or blades, in the planeof the polygon rail, and being hereinafter referred to as the pivot leg; the device including also a pivot pin or stem passed through the outer end of the pivot leg, and adjustable pencil stopsmounted upon the polygon and circle rails, for laying out the lengths of the sides of polygon figures of varying size or area, and for drawing circles of varying diameters.

A still further object is to provide a drafting instrument of the kind referred to, T-shaped in plan, the upper stem being designated as a poly-' gon rail or blade and a circle rail or blade, combined as a unit, the said polygon rail or blade being spacedly calibrated from its ends inwardly to its center point, and correspondingly and consecutively numbered, the said circle blade or rail being similarly calibrated with consecutively numbered calibrations, from its center'point outward to the ends of the blade, whereby either polygons or circles may be laid out and drawn as desired by means of adjustable pencil stops slidably mounted on the unit; the lower and medial stem of the T-shaped device being designated as a pivot stem or leg, the same having a pivot pin passed through its outer end whereby the device may be rotated in use for laying out the different figures.

With the foregoing objects in view, together with such other objectsand advantages as may appear from the specification, attention is directed to the accompanying drawing as embodying a preferred form of the invention, and wherein:

Figure -l is a perspective View of the drafting instrument or polygon square, constructed according to this invention. a

Figure 2 is a top plan View of the instrument,

here shown however as somewhat longer than as shown in Figure l.

Figure 3 is anend elevation of the instrument, drawn on a-s lightly enlarged scale.

The invention comprises an angular work or layout bar referred to generally at 5, the same being made of metal or other suitable material, and of. any desired dimensions as required in use. This bar or unit 5 is right-angled in cross section, and includes the narrow, elongated and flat polygon blade or rail 6, formed with a straight scribing or marking edge 5a, and a similar circle blade or rail '1 extended at right angles from the proposed rear margin of the polygon blade. The polygon blade 6 is spacedly calibrated along its upper side vor'face and outer margin, from its ends to its central point C, the said calibrations being indicated at 8, and being numbered consecutively from'the ends inwardly to the point C, the saidnumbering running from 3 to 20 as shown in the drawing, for laying out polygons of three sides upward to twenty sides. Thus these calibrations are spaced apart and numbered to correspond with and for gaging the required number of sides and the lengths of the sides of the various polygons designed to be embraced within thescope of the instrument. Thus it will be noted that the spacing of these calibrations gradually and regularly diminishes from the ends inwardly towards the center of the blade, as would naturally be necessitated by the increasing number of sides and reduction of di-- ameters or areas of the figures of the polygons. Similarly the circle blade I is demarked or calibrated along its inner face or side with a plurality of equi-spaced calibrations 9, consecutively numbered from the center point C outwardly to the ends of the blade. As shown in the drawing, the central calibrations of the circle blade I, at each side of the point C are numbered as 12, and the outer ones 'at the ends of the blade as 25, for the purpose of gaging and drawing circles of varying diameters, and as to be explained later.

A pair of adjustable stop lugs It, Illa, looped centrally as at lilb, are by these looped portions slidably seated astraddle the vertical circle rail or blade 1, these lugs being provided with preferably integrally formed stop fingers or pencil stops We extended from the ends of the outer legs of the lugs, slidably across the face of the blade 5, the extremities of these fingers ltc overlapping and projecting beyond the marking edge 6a of the blade 6, to complete the said pencil stops as aforesaid. Blocks l I are welded or otherwise secured to the outer sides of the inwardly disposed legs of the lugs It, "is, and these blocks as well as the attached lugs are tapped through for threadedly engaging thumb-screws [2, adapted to bear against the blade 7, whereby the stops may be releasably locked at any adjusted position along the blade I.

A flat and elongated pivot stem or leg I3 is rigidly joined by its inner end centrally and perpendicularly to the back of the unit 5, and is extended back in the plane of the polygon blade 6, with the axis of this leg co-inciding with the center point C of the unit 5 comprising the rails or blades 6 and l. The outer end of the leg I3 is rounded and is tapped through on its axial line to engage the pointed and threaded end of the pivot pin or stem M, with the point thereof protruded downward as shown, and a hand or finger knob I5 is mounted at the upper end of this pin, for facilitating the use of the instrument.

In the construction of this instrument as described, the length of the pivot leg [3 is so proportioned to the spacing of the calibrations of the polygon blade or rail 6, that the like consecutive numbers of these calibrations, at each side of the center point C and the spaces between the same, will correspond with and measure the lengths of the several sides of the polygon to be drawn by that instrument rotating upon the pivot leg and pivot pin, with the pivot leg as a radius, in which process the numbers or numerals of the calibrations'opposite which the pencil stops are located, will also indicate the number of sides that the polygon will embrace. In other words the distance between any two similarly numbered calibrations at each side of thecenter point C, will represent the length of each side of the polygon, while the numerals themselves will indicatethe number of sides in the completed polygon. In laying out the calibrations on "the polygon blade 5 for drawingpolygons having various numbers of sides. it is'evidcnt that the several sides comprising the perimeter of any required polygon, would-be co-equal in length, and would all tangentially circumscribe a circle drawn on a radius equalling the spacing of the pivot point I4 from the outer center point C on the blade 6, and that each of thesides of the circumscribed polygon would be tangent at its exact center point to the inscribed circle, with a radius of that circle contacting each side perpendicularly at this same central point'of contact, and forming at each side of the radius a right angle, that is to say a right angle at either side of the center point C on the blade 6. It is evident that the value of the several co-equal angles subtended at the center of the polygon would equal the 360 degrees of the circle divided by the number of sides of the polygon desired, and that at each successive relocation of the blade 6 in drawing the polygon. a right angled triangle would be defined or indicated by the constant radius of the pivot leg l3, and that the center angle for each right angled triangle would be determined as aforesaid by the number of sides of the polygon divided by 2. Theright angled triangle might be completed by another radial'line cutting the circle and meeting the extremity of the adjacent leg of the right angled triangle as thus constructed at that side of the center point C, this leg constituting one-half of the side of the polygon being estimated, the other half lying on the opposite side of the center point C. With the inner angle and the length of the side at the right angle known, the common length of the several sides of the polygon being estimated, may be readily ascertained by application of the usual mathematical formulas as commonly employed in such work. That length is then calibrated upon the blade 6, one-half thereof at each side of the center point C. This process is repeated progressively for calibrating the lengths of sides of the other polygons having various numbers of sides, to the extent desired. Likewise as to the other calibrations as numbered, and the spacing sub-tended between any two-similarly numbered calibrations at each side of the center point C.

Thus the-capacity of' the tool for describing polygons of a fixed diameter or area, as deter mined by the length'of the pivot leg l3, would range from a three-sided polygon or triangle, with each side of a length corresponding to the distance between the calibrations numbered 3" at eachend of the blade 6, up to the twentysided polygon above referred to. In the drawing of circles, and withthe assumed length of the pivot leg placed at six inches, the diameters thereof would range from twelve inches, as shown by the calibrations numbered 12 at the center of the blade 7, up to a diameter of twenty-five inches, as indicated by the calibrations numbered 25 at the ends of the blade. the tool as shown in the drawing, is capable of drawing polygons and circles of certain diameters and areas, but these diameters and'areas. may be extended by lengtheningthe pivot leg l3 and the'unit 5, and correspondingly rear;

ranging and spacing the calibrations of the polygonand circle blades 6 and 1. Larger sizes of polygons may also be drawn by extending lines from the center of a smaller figureoutwardlythrough the points of intersection of the several sidesthereof to the required lengths, and then connecting the outer ends of these lines by lines paralleling the inner lines of the original figure. In the drawing of circles, the required radius is taaken by a compass, by placing the point of one compass leg at the point of the pivot pin 14, and the point of the other compass leg at the, desired number of calibration on the circle blade I, at either side of the center thereof, and then moving one of the pencil stops I00 so as to align its inner edge with such calibration. is then located against this stop and is rotated with the instrument around the pivot pin M, the point of the latter being properly positioned upon the surface on which the circle is to be drawn, the pencil point of course being in Contact with this surface. 1

Itis thought that the construction and use of the polygon square or drafting instrument con;-

In other words, 7

A pencil stituting the subject matter of this invention, will be fully understood from the foregoing description, and While I have herein shown and described a specific embodiment of the invention and specific structural features thereof, it is understood of course that the same may be changed or varied, within the scope of the appended claims,

I claim:

1. A device of the kind described, the same being generally T-shaped in plan, the upper crossstem thereof being in the form of an elongated, straight-edged work bar or lay-out bar, right angled in cross-section and including a relative-- ly narrow and flat polygon blade for laying out the sides of polygon figures, and a similar circle blade perpendicularly extended along a margin of the polygon blade, for drawing circles, the medial lower stem of the device carrying a pivot pin at its free outer end, Whereon the device may be rotated in laying out the various figures.

2. A device of the kind described, the same being generally T-shaped in plan, the cross-stc1n thereof being right-angled in cross section, one blade, thereof constituting a polygon blade and the other blade a circle blade, these said blades being calibrated at each side of the center points thereof for laying out polygons of various numbers of sides and areas and circles of various diameters and areas, the medial stem thereof forming a pivot leg, a pivot pin passed through the outer free end of the pivot leg and about which the instrument may be rotated upon the work, for laying out polygons and circles of varying sizes.

3. In a device of the kind described, the same being generally T-shaped in plan, the cross-stem thereof being right-angled in cross-section and including in combined form a polygon blade and a circle blade, the said polygon blade being spacedly calibrated from its ends inwardly to its central point and correspondingly and consecutively numbered with like numbers opposite calibrations equi-spaced from said central point, the

circle blade beingsimilarly calibrated with consecutively numbered calibrations from its central point outward to the ends of the blade, for laying out polygons or circles oi various sizes, adjustable stops slidably mounted on the said cross stem of the device, for gaging the lengths of sides of polygon figures and the diameters of circles, the central stem of the device constituting a pivot leg, and a pivot pin passed through the free end of the pivot leg and about which the instrument may be rotated upon the work in the process of laying out the figures of polygons and circles.

HERALD B. HIDY. 

